The present invention relates to a mobile terminal and for example, can be applied to a mobile terminal that transmits information on privacy, such as identification information and status information, between mobile devices.
In recent years, aiming at a reduction in the number of persons killed in traffic accidents, discussion of vehicle-to-vehicle or road-to-vehicle communication for the purpose of safe driving support is in progress. In the safe driving support service, a vehicle, such as an automobile, transmits vehicle information around and also detects a risk of traffic accident, such as collision and rear-end collision, based on vehicle information received from vehicles around and vehicle information of the own vehicle and notifies a user of the risk. Here, the vehicle information refers to a combination of identification information for identifying a mobile device and status information indicating the status of a vehicle, such as position, moving speed, and moving direction.
Because the vehicle information is information on privacy and a device existing in a communicable range with the vehicle can receive the vehicle information, there is a possibility that the vehicle information is misused for the purpose other than the safe driving support. Specifically, in the case where a vehicle tracking a specific vehicle has lost sight of the vehicle at an intersection etc., the vehicle identifies the location of the vehicle being tracked from the received vehicle information and resumes tracking. As described above, if the information to be used for the safe driving support is used easily for a purpose different from the original purpose, it is not possible to obtain trust to the service from users, which prevents the safe driving support service from being spread. Consequently, it is important to prevent vehicle information from being misused. As methods for protecting vehicle information flowing through a communication path, the following techniques are known.
In Japanese Patent Laid-Open No. 2006-174179 (Patent Document 1), as for a vehicle-to-vehicle communication device, another vehicle acquires a vehicle ID for identifying the individual vehicle at the time of vehicle-to-vehicle communication, and thus in order to prevent personal information from being leaked, a period of validity is set to the vehicle ID to be issued and distributed, and each time the period of validity expires, the vehicle ID is updated.
In Japanese Patent Laid-Open No. 2010-204982 (Patent Document 2), the identification information for identifying an own vehicle is updated with a predetermined timing (identification information update function). Then, when the identification information for identifying the own vehicle is updated, if it is determined that the traveling condition of the own vehicle is “proximity condition”, the update of the identification information of the own vehicle is prohibited (identification information update function).
In “Illustrated RFID Textbook—All about Wireless IC Tags Directed to Ubiquitous Society—, editorial supervisor Junichi KISHIGAMI, first edition, published by ASCII corporation, Mar., 4th in 2005, p. 166-181” (Non-Patent Document 1), identification information is encrypted by using public key cryptography. In the case of the public key cryptography, the side that encrypts information (information transmission side) needs a public key and the side that decodes the information (information reception side) needs a secret key corresponding to the public key. At first, the information reception side holds a public key and a secret key corresponding to the public key and transmits the public key to the information transmission side. The device on the information transmission side generates a random number and then encrypts the identification information by the public key together with the random number. Then, the device sends the encrypted value and random number to the device on the information reception side. The device on the information reception side decodes the encrypted value by using the secret key and the received random number and acquires the identification information.
Further, Non-Patent Document 1 also describes the system for finding a hash function. The device on the information transmission side finds a random number (or time information) and a hash value of identification information and sends the random number and the hash value. The information receiving device stores the identification information of the device on the information transmission side in advance. Then, the hash value is obtained from each piece of identification information and the received random number (or time information) and the identification information that agrees with the received hash value is retrieved.
In “RFC2010-204982 Privacy Extensions for Address Configuration in IPv6” (Non-Patent Document 2), the identification information of the device is updated periodically.